For some communication devices which have to transmit real time data or at least data in correspondence with a given time, it is necessary to provide an accurate real time clock. This can be done remotely by sending over the air information for setting an accurate real time clock.
It is the case for instance in the domain of utility electricity meters, in which different regulations and demands for accuracy of the real time clock exist in different countries. In Sweden, where there is a strong demand for communicating meters, it is a legal requirement for some types of meters to be programmed within ten seconds of the actual date and time. Some customers even demand a higher accuracy than this, and require that the real time clock is programmed within seven second of the actual date and time when their clock is set remotely. In many communication systems, there are predictable delays between sending data to a remote device and the device receiving the data, allowing the time and date to be set on the device by a communication system reliably. However, in other communication systems of the type using GPRS or SMS bearers over a radio communication network, this is not the case. More generally, when data are transmitted over a radio communication network through communication packet data, it is not possible to rely on the delivery time for data.